CAMBIOS TEMPORALES EN LA DIETA DEL PLAYERO ROJIZO (CALIDRIS CANUTUS RUFA) EN UN HUMEDAL DE PENÍNSULA VALDÉS, PATAGONIA ARGENTINA

Abstract

Temporal variation in the diet of the Red Knot (Calidris canutus rufa) in a wetland from Península Valdés, Patagonia Argentina. – During their northward migration, Red Knots forage extensively in intertidal areas of Península Valdés (Patagonia, Argentina). This species has a small population and declines have been linked to reduced prey availability in migratory stopover sites. Thus, knowing the temporal variation in prey availability and diet is essential to understand population dynamics in the Red Knot. We studied temporal variation in the diet of the Red Knot at Colombo Beach (northeastern Nuevo Gulf, Península Valdés). To evaluate prey availability, we sampled benthic invertebrates in March every study year. We collected 292 feces during April in 2002, 2003, 2006, and 2007. Prey items were identified by using key hard structures. The clam Darina solenoides was the most common prey positively selected every year (Savage index), although in some years the polychaete Travisia olens was also selected. Other, less important prey items were seeds, mussels, insects, crustaceans, isopods, amphipods, ostracods, the snail Buccinanops globulosus, and the clam Tellina petitiana. Red Knots selected clams in variable size ranges depending on the year (10–18 mm in 2002, 8–22 mm in 2003, 10–20 in 2006, and 18–26 mm in 2007 mm). In the years where the contribution to biomass by the clam D. solenoids was lower, knots had a higher trophic diversity. Diet composition varied between years mainly due to differences in the intake of polychaetes.